[I]nstead of constantly griping about having to type Hirb.enable, I found how to automagically load it in the Rails console:
1. In your home directory [ ~ ], type subl .irbrc
2. Paste in this bit:
if defined?(Rails) && Rails.env
3. Save and enjoy*.
*Confirmed working with OS X 10.6.8 and [Rails] 4.0.2
Yes, my OS is old and janky - stop laughing.
via Poop’s comment at http://tagaholic.me/2009/09/07/hirb-tips-for-rails.html